Electromagnetic relay



July 18, 1939. c. H. LARsoN ELECTROMAGNETIC RELAY Filed July 21, 1956.Patented July 18, 1939 i UNITED STATES PATENT OFFICE n ELECTROMAGNETICRELAY Carl H. Larson, Elkhart, Ind.

Application July 2l, 1936, Serial No. 91,725

14 Claims.

In relays heretofore known, and particularly in mechanical relays, ithas been the practice, when a plurality of switches were to be operatedfrom. the same magnetic circuit, to mount the several contacts on acommon armature, so that all switches would act in unison. If thecircuit controlled by any one pair of contacts required a time delay,those contacts were arranged to operate from an entirely differentmagnetic circuit,

l0 for the common way to eilect a time delay in a mechanical relay otherthan by clock work is to provide the iron circuit with a secondaryclosed winding.

'Ihe principal object of this invention isto provide an electro-magneticrelay in which fast acting and slow acting contacts may be associatedwith the same magnetic circuit, or with a plurality of magnetic circuitsof equivalent characteristics, and in which the slow acting contactsneed not necessarily have the same time delay characteristics.

Stated otherwise, it is the principal object oi the invention to providean electro-magnetic relay in which a single magnetic circuit, or aplurality of magnetic circuits of equivalent characteristics, operate aplurality of contacts having an inilnite variety o! time delaysincluding contacts which are immediately responsive to the flux set upthrough the magnetic circuit or circuits.

Other objects of the invention are to provide a relay which is cheap tomanufacture, small in size, easy to adjust, and in which the contactelements may be readily replaced, if occasion demands.

Still flu'ther objects and advantages will become apparent as thedisclosure proceeds'and the description is read in conjunction with theaccompanying drawing, in which Fig. 1 is a plan view of the relayembodying this invention;

Fig. 2 is a vertical, sectional view on the line 2--2 oi' Fig. 1;

Fig. 3 is a sectional view taken on the line4 3--3 of Fig. 1, throughthe switch B, the switch parts being shown in the position whichtheyassume immediately after energization of the coil;

Fig. 4 shows the position of the parts of switch B immediately after thecoil has been de-energized; and Y Fig. 5 shows, by way ofillustration,-an electrical circuit associated with the relay.

It will be understood that this specic disclosure is by way ofillustration only, and that the invention may be embodied in many otherforms within the scope of the appended claims.

(CI. 20o-97) The relay shown inthe drawing comprises a coil III whichhas an axial opening II adapted to receive an iron core I2 whichconstitutes a part of the magnetic circuit operating switches A,

B and C. The magnetic circuit also includes top 5 and bottom pole piecesI3 and I4, respectively, each of which is segmental in form and has ahole I5 adapted to receive the reduced end of the core I2. The polepieces are held in place by washers I6, secured by screws I1, threadedinto 10 tapped holes in the core.

A pluralityl of alined apertures I8 and I9 are provided in the top andbottom pole pieces, respectively, to receive the switches A, B and C.

Pole sleeves 20 and 2i are iitted into the aper- 15 tures I3 and I3 toiix the position of the air gap 22 associated with each switch.Preferably a vertical split sleeve 23 of non-magnetic material, such asBakelite, brass, or the like, is tightly telescoped over each switch atthe air gap to 20 hold the switch in its proper position with respect tothe magnetic circuit and to keep the pole sleeves 23 and 2I in place.

Of course it will be understood that the parts comprising the magneticcircuit, i. e., the core, 35 the pole pieces and the pole sleeves, areall oi suitable magnetic material, such as high quality Swedish iron. y

A tube 24 is telescoped over each switch with its associatedpolesleeves, and it extends from 30 pole piece to pole piece. These tubesprotect the switches from damage, together with a cover plate 25 held inplace by screws 26, and a bottom terminal box 21 consisting of a.block28 of insulating material, and a bottom closure 29, the two being 35secured to the iron circuit by screws 30. The switches, therefore, whenin their assembled position, are completely enclosed and are not subjectto tampering by unauthorized persons.

For the purpose of illustration, the switches A 40 and B have been shownas slow make, quick break switches (the time interval for closing thecircuit through switch A being somewhat longer than that required forclosing the circuit through switch B), and switch C has been shown as a4 fast acting switch in both making and closing the electrical circuit.All three switches are of the type which include a switch envelope 3|through the base of which a pair of electrodes are sealed, one beingconstantly in contact with 50 a mercury ll 32 within the switch, and theother being intermittently placed in contact with the mercury (and hencethe other electrode) by the action of a displacer 33 which includes a,glass thimble 34 open at its top, as indicated at 35, 55

and an iron sleeve 36 which acts as an armature of the switch. Springs31 and 3B cushion'the armature in its movement within the switchenvelope, and it will be understood that when the coil I0 is energized,the armature is drawn downwardly, causing mercury to be displaced forclosing the electrical circuit through the electrodcs, and converselywhen the coil ill is deenergized, the armature is restored to itsnormally raised position for opening the circuit through the electrodes.

Switches A and B diier from switch C in that a time delay element 39 isinserted in the opening 35 at the top of the thimblel 34, ,the elementpreferably being a porous plug of suitable material such as Alundum(Grade RA 84, RA 360 or RA 98) a product of the Norton Company,Worcester, Massachusetts, or similar material.

The plug is fused into place so that gas entrapped within the thimbleduring the downward movement of the dlsplacer slowly escapes through thetimedelay element, which has the effect of retarding the movement ofmercury toward the bared end of the central electrode. This action isshown in Fig. 3 where the coil has just been energized, causing thedisplacer to move downwardly and trap gas within the thimble to forcethe mercury away from the central electrode. As the gas pressure on theinside and outside of the thimble slowly equalizes, the mercury levelgradually rises until the mercury level within the thimble finallyreaches the bared end of the central electrode.

It will be observed that the central electrode of the switch B issomewhat shorter than the corresponding electrode of the switch A sothat if the porosity of the plugs 39 in both switches is the same, thecircuit through the electrodes of the switch B will be closed prior tothe closing of the circuit through the switch A.

When the coil lll is de-energized, all the displacers rise to theposition in which they are shown in Fig. 2, switches A and B, however,momentarily carrying up within their armatures a quantity of mercurywhich tends to keep the circuits through these switches closed, butwhich is prevented from having this effect by reason of an' aperture 40provided in the side of the displacer, this aperture allowing gas toenter the displacer as soon as the outside mercury level has droppedbelow it, and as this takes place almost simultaneously with thede-energization of the coil I0, the result is that switches A and B aswell as switch C, effect a quick break of their respective circuits uponde-energization of the coil l0.

There are many circuits in which it is desirable to employ thecombination of fast and slow acting switches, and one such example is amotor starting circuit; such as shown in Fig. 5. The motor is indicatedat 4| and is energized from a suitable source of electromotive force 42.Starting resistances 43 and 44 are provided, which are under the controlof the mercury switches A, B and C of the control relay, generallyindicated at 45. The side electrode of switch C is connected to thecentral electrode of switch B, and the side electrode of switch B isconnected to the central electrode of switch A, so that the resistance43 parallels the electrodes of switch B, and the resistance 44 parallelsthe electrodes of switch A. The coil I0 of the relay 45 is energizedfrom a battery 46, or other source, and a switch 41 is provided inseries with the coil. When the switch 41 is closed to energize the coilI0, the armatures of all three switches A, B -and C are drawndownwardly,and since switch C is a fast acting switch, current isimmediately sent through the motor 4| through resistances 43 and 44(switches A and B at this instant being open, due to the time delayelements associated with the armatures). As soon as the time delayelement of switch B has completed its function so that the electrodes ofthat switch are bridged with mercury, the resistance 43 is therebyshunted closed again, the starting resistances are automatically throwninto the motor circuit.

It will be understood that in the practice of this invention, it is notessential that the same magnetic circuit be used for operating theseveral switches, for obviously separate magnetic circuits of equivalentcharacteristics might be employed. For example, if the magnetic circuitsassociated with the switches A, B, C and D in Larson Patent 1,967,951are all identical in every respect, the several switches may havedifferent time delay characteristics. In other words, switches A and Bmay be fast acting switches, and switches C and D may be slow act ingswitches.

In the appended claims, the expression a magnetic flux of givencharacteristics" is used. This expression is intended to denote the timerelationship between the building up of a magnetic iiux and theoperation of the switch armatures. In other words, a magnetic flux ofgiven characteristics is a flux which will cause the amature of anyswitch associated with it to move at a given instant after apredetermined magnetomotive force has been set up.

I claim:

1. In a relay, means for producing a magnetic flux of givencharacteristics, a pair of switches associated with the means andoperated thereby, one of the switches comprising a switch envelopecontaining a quantity of mercury adapted under certain conditions toprovide an electrical path between spaced electrodes in the envelope,means controlled by the flux producing means for manipulating themercury to eiect a change in the electrical circuit through theelectrodes, a time delay element in the envelope adapted to provide atime interval between the actuating of the mercury manipulating meansand the changing of the condition of the circuit through the electrodes,the other switch also being actuated by the flux producing means andhaving a time characteristic diiierent from the rst mentioned switch.

2. In a relay, means for producing a magnetic flux of givencharacteristics, a pair of switches associated with the means andoperated thereby, one of the switches comprising a switch envelopecontaining a quantity of mercury adapted under certain conditions toprovide an electrical path between spaced electrodes in the envelope,means controlled bythe ux producing means for manipulating the mercuryto effect a change in the electrical circuit through the electrodes, atime delay element in the envelope adapted to provide a time intervalbetween the actuating of the mercury manipulating means and the changingof the condition of the circuit through the electrodes, the other switchalso being actuated by the flux producing means and including a timedelay element capable of eiecting a time delay in the condition of thecircuit through said other switch which is different from'the time delayeffect in the iirst mentioned switch.

3. In a relay, a magnetic circuit including pole pieces, a coreconnecting them, and a coil for energizing the circuit, a pair ofswitches associated with the magnetic circuit and operated thereby, oneof the switches comprising a, switch envelope containing a quantity ofmercury adapted under certain conditions to provide an electrical pathbetween spaced electrodes in the envelope, means responsive to" themagnetic circuit for manipulating the mercury to effect a change in theelectrical circuit through the electrodes, a time delay element in theenvelope adapted to provide a time interval between the actuating of themercury manipulating means and the changing of the condition of thecircuit through the electrodes, the other switch also being actuated bythe magnetic circuit and having a time characteristic different from thefirst mentioned switch.

4. In a relay, a coil, an iron core through the coil, top and. bottompole pieces projecting laterally from the ends of the core, and aplurality of switches operatively associated with the pole pieces forresponse to the coil, one of said l switches including a time delayelement and another being immediately responsive to the coil.

5. In a relay, a coil, an iron core through the coil, top and bottompole pieces projecting laterally from the ends of the core, and aplurality of switches operatively associated with the pole pieces forresponse to the coil, one of said switches including a time delayelement and another having a time delay element of diiIerentcharacteristics than the time delay element of the rst named switch.

6. In a relay, a coil', an iron core through the coil, top and bottompole pieces attached to the ends of the core, said pole pieces beingsegmental in form and having alined apertures, a mercury switchincluding a vertically movable armature mounted in the apertures, andpole sleeves associated with the pole pieces forfixing the position ofthe air gap.

7. In a relay, a coil, an iron core through the coil, top and bottompole pieces attached to the ends of the core, said pole pieces beingsegmental in form and having a plurality of alined apertures and aplurality of mercury switches mounted in the apertures and includingvertically movable displacers shiftable in response to the coil, one ofsaid switches being slow acting and another being fast acting.

8. In a relay, a coil, an iron core through the coil, top and bottompole pieces attached to the ends of the core, said pole pieces beingsegmental in form and having a plurality of alined apertures and aplurality of mercury switches mounted in the aperture and includingvertically movable displacers shiftable in response tol the coil, polesleeves associated with `each switch for fixing the position of the airgap, a tube mounted over each switch and its respective pole sleeve andextending from pole piece to pole piece, and means for closing the topand bottom of the apertures so as to completely enclose the switches.

9. In a relay of the class described, means for producing a magneticflux of given characteristics, and a plurality of switches mounted inoperative relation to said means, one of said switches being fast actingand another being slow acting, the latter comprising a stationary switchenvelope, spaced electrodes in the envelope, a mercury fill adapted tobe manipulated to lmake or break an electrical circuit through theelectrodes, and a time delay element adapted to restrain the movement ofmercury toward circuit opening position.

10. In a relay of the class described, means for producing a magnetic uxof given characteristics, and a plurality of switches mounted inoperative relation to the said means, one of said switches being fastacting and another being slow acting, the latter comprising a stationaryswitch envelope, spaced electrodes in the envelope, a mercury filladapted to be manipulated to make or break an electrical circuit throughthe electrodes, and time delay element adapted to restrain the movementof mercury toward circuit closing position.

11. In a relay of the class described, means for producing a magneticflux of given characteristics, and a plurality of switches mounted inoperative relation to said means, one of said switches being fast actingand another being slow acting, the latter comprising a stationary switchenvelope, spaced electrodes in the envelope, a mercury ll adapted to bemanipulated to make or break an electrical circuit through theelectrodes, a displacer responsive to the ux producing means forshifting the mercury level, and a time delay element adapted to restrainthe movement of mercury toward circuit opening position.

12. In a relay of the class described, means for producing a magnetic uxof given characteristics, switch means mounted in operative relation tosaid flux, said switch means including a quantity of mercury, a pair ofelectrodes, flux responsive means shifting the mercury to change thecondition of the electrical circuits associated with the electrodes, anda time delay element adapted to restrain the movement of mercury in thevicinity of one of the electrodes whereby a time interval takes placebetween the operation of the flux responsive means and the changing ofthe electrical circuit associated with said one electrode, the otherelectrode being immediately responsive to the action of said fluxresponsive means.

13. In a relay of the class described, means for producing a magneticflux of given characteristics, switch means mounted in operativerelation to said flux, said switch means including `a quantity ofmercury, a pair of electrodes, flux responsive means shifting themercury to change the condition of the electrical circuits associatedwith the electrodes, and a time delay element adapted to restrain themovement of mercury in the vicinity of one of the electrodes whereby atime interval takes place between the operation of the flux responsivemeans and the changing of the electrical circuit associated with saidone electrode, said flux responsive means effecting a change in theelectrical circuit associated with said other electrode, other thansimultaneously with the change eiiected with respect to said iirstelectrode.

14.'In a relay, means for producing amagnetic ux of givencharacteristics, a plurality of pairs of contacts associated with andresponsive to said means. at least one of said pairs including a timedelay element adapted to introduce a specified time interval beforeaiecting the circuit which said pair of contacts control, another ofsaid pairs of contacts being alienated to aect the circuit which thelatter pair control at a time interval, if any, which is substantiallydifferent than that eiected by said rst pair of contacts.

CARL H. LARsoN.

